This invention relates generally to the welding of metal components. More particularly, the present invention relates to a spot-welded interconnection method of two or more conductive tabs.
The preferred method of mechanically and permanently joining two pieces of sheet metal tab stock for electrical connections in batteries and other electronic devices is resistance spot welding. Currently, copper spoons are used in production welding to join two thin metal tabs together by spot-welding the tabs and spoon to make a satisfactory electrical connection between the tabs. To reliably join two tabs in a parallel weld to form a conductive interconnection, a third layer of conductive material, such as copper, is required to shunt the proper amount of current through the two tabs being joined to form a structurally-sufficient weld nugget.
The use of the spoon in welding the tabs together causes several difficulties in the manufacturing process. The created spot-weld is not particularly strong, i.e. the tabs can be pulled apart fairly easily, and the breaking of the weld will open an electrical circuit. Further, using a spoon in the welding process adds an additional opportunity for error and requires manufacturing personnel to align the tabs and place copper spoon between the tabs while keeping them aligned during the welding process, which thus increases manufacturing time.
Moreover, it is common to weld the tabs and spoon by hand with a welding device and the error rate from human operation increases the likelihood of an improper weld. The weld itself is a difficult one to make as most welding devices use electrodes to weld, and in welding the tabs and spoon, the electrodes have a tendency to stick to the tabs and spoon after the weld is made, which makes the removal of the electrodes from the weld a delicate process without deleteriously affecting the weld. Furthermore, a xe2x80x9ccoldxe2x80x9d weld will occur if the operator forgets to use the spoon, and this will provide a connection that does have adequate mechanical joint strength. There is also an increased probability of a completely unsatisfactory weld if the operator incorrectly aligns the tabs and spoon immediately prior to welding, and in such case, the tabs and spoon can be destroyed or rendered completely unusable by the failed weld attempt.
A further problem is that once the weld is made with the copper spoon, the spoon requires maintenance to prevent corrosion and deterioration. If the spoon is allowed to deteriorate, the electrical connection will be broken over time and this shortens the life of the battery or electrical device that the welded tabs are part of.
Accordingly, it would be advantageous to use a method to weld a pair of electrical tabs together that does not require the use of a spoon, or conductive material. It would also be advantageous for such method to use a simplified weld whereby the weld can either be accomplished through and automated process or very easily by a person. It is to the provision of such an improved method of spot-welding a pair of conductive tabs together that the present invention is primarily directed.